Abstract Background This systematic review has two purposes: to consolidate the current knowledge about clinical effectiveness of electrochemotherapy, a highly effective local therapy for cutaneous and subcutaneous tumors; and to investigate the differences in effectiveness of electrochemotherapy with respect to tumor type, chemotherapeutic drug, and route of drug administration. Methods All necessary steps for a systematic review were applied: formulation of research question, systematic search of literature, study selection and data extraction using independent screening process, assessment of risk of bias, and statistical data analysis using two-sided common statistical methods and meta-analysis. Studies were eligible for the review if they provided data about effectiveness of single-session electrochemotherapy of cutaneous or subcutaneous tumors in various treatment conditions. Results In total, 44 studies involving 1894 tumors were included in the review. Data analysis confirmed that electrochemotherapy had significantly ( p  < .001) higher effectiveness (by more than 50%) than bleomycin or cisplatin alone. The effectiveness was significantly higher for intratumoral than for intravenous administration of bleomycin ( p  < .001 for CR%, p  = .028 for OR%). Bleomycin and cisplatin administered intratumorally resulted in equal effectiveness of electrochemotherapy. Electrochemotherapy was more effective in sarcoma than in melanoma or carcinoma tumors. Conclusions The results of this review shed new light on effectiveness of electrochemotherapy and can be used for prediction of tumor response to electrochemotherapy with respect to various treatment conditions and should be taken into account for further refinement of electrochemotherapy protocols.